Kaffe integration

[Nic Ferrier]

java.lang.Throwable depends on:

   gnu.vm.stack.StackTrace 
   gnu.vm.stack.StackFrame

so I think that one of 2 things needs to be done to allow VM
integration:

- a requirement to implement gnu.vm.stack classes
- a requirement to implement java.lang.Throwable


It seems to me that the former is the best plan. This just means that
the vm-integration page on the website needs to be updated to state
clearly that the package:

   gnu.vm.stack 

needs to be implemented (and probably "there is an example
implementation (for japhar) in vm/reference").


Nic